[clang] [llvm] [X86] Reduce -ffixed-r compile-time overhead (PR #184606)

[via cfe-commits]

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@@ -516,14 +516,16 @@ BitVector X86RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   Reserved.set(X86::SSP);
 
   auto &ST = MF.getSubtarget<X86Subtarget>();
-  if (ST.is64Bit()) {
-    for (size_t Reg = 0; Reg < getNumRegs(); Reg++) {
-      // Set r# as reserved register if user required
-      if (ST.isRegisterReservedByUser(Reg)) {
+  if (ST.is64Bit() && ST.hasUserReservedRegisters()) {
+    // Set r# as reserved register if user required
+    for (unsigned Reg = X86::R8; Reg <= X86::R15; ++Reg)
+      if (ST.isRegisterReservedByUser(Reg))
+        for (const MCPhysReg &SubReg : subregs_inclusive(Reg))
+          Reserved.set(SubReg);
+    for (unsigned Reg = X86::R16; Reg <= X86::R31; ++Reg)
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zhouguangyuan0718 wrote:

Done

https://github.com/llvm/llvm-project/pull/184606